Treatment of cellulosic material with apo-thiourea flame resistance and the resulting material

ABSTRACT

Cellulosic material is fire-proofed by impregnation with an aqueous solution comprising tris(1-aziridinyl) phosphine oxide (APO) and thiourea of a C1-4 alkyl, methylol or ethylol thiourea, followed by curing.  Thioureas specified are 1,3-dimethyl, 1,3-diethyl, 1,3-diethylol, 1-ethyl, 3-ethylol, and 1-methyl, 3-n-propyl thiourea. The solution may also contain an APO polymerization catalyst, other fire-proofing agent, textile softener, or wetting agent.  Other fire-proofing agents specified are methyl and ethyl ammonium phosphate and urea.  The cellulosic material may be of cotton, rayon, cellulose acetate, jute, rope, paper, cardboard, or wood.  The mole ratio of APO/thiourea may be 0.3-3.0 to 1.  The aqueous solution may contain 15-50% of mixture.  The pick up may be 30-120 gm of solution per 100 gm of material.

United States, Patent ()7 ABSTRACT OF THE DISCLOSURE A method for rendering cellulosic textiles durably flame retardant, even after repeated laundering, comprising treating the textiles with an aqueous solution containing a miXture of thiourea and tris(l-aziridinyl) phosphine oxide (APO).

This invention relates to an improved composition and method for the treatment of cellulose and/or cellulosic-containing materials. More particularly, the present invention relates to the treatment of cellulose-based or cellulose-containing woven and non-woven textiles (such as cotton and rayon), paper, wood, cardboard, rope and jute with a mixture containing tris(1-aziridinyl)phosphine oxide and at least one thiourea compound.

The use of tris(1-aziridinyl)phosphine oxide (APO) in combination with urea for the production of flame resistant textiles is disclosed, for example, in US. Patent 2,859,134 to Reeves et al. A process for fixing pigments on fibrous materials using a mixture of urea precondensation products and polyfunctional ethylenimine compounds is disclosed in US. Patent 2,961,349 to Bartl et al. One

of the disadvantages of such processes, however, is that comparatively large amounts of expensive APO are required in order to obtain good flame retardant properties. While a good finish is obtained when the active ingredients of the treating bath .consist of ureaand APO, the durability of the finished textile to laundering is low and the treating chemicals are removed after several laundering cycles. Furthermore, odoriferous volatile products of undetermined composition are formed during the curing step when a mixture consisting of urea and APO is employed in the treating composition.

It has now been found that the amounts of APO required to achieve satisfactory flame-retardance for various cellulosic materials (especially woven and non-Woven textiles) can be reduced considerably by using mixtures of thiourea (and/or substituted thiourea compounds) along with APO as the major components of the treating composition.

In the case of cellulosic textiles, the finished cellulosiccontaining fabric has better fiber strength and retains its finish much longer than can be achieved with other APO- containing compositions. Another advantage of the invention is that dye shade changes in fabrics either do not occur with APO-thiourea treating compositions, or else occur uniformly over the fabric during treatment.

According to the present invention, a mixture of a thiourea compound and APO is incorporated into a treating bath and a cellulosic-containing material is impregnated with the bath composition. The impregnated material is then cured to form a flame-resistant product.

In a specific embodiment of the present invention, a

3,376,160 Patented Apr. 2, 1968 mixture containing a thiourea compound and APO in a mole ratio of from about .3:1 to 3:1 (preferably from about .5 :1 to 2:1, thioureazAPO) is dissolved or dispersed in a solvent such as Water to form a treating bath in which the concentration of the combined thiourea- APO composition is from 15 percent to percent by weight based upon the total weight of the treating bath. Although a catalyst is not necessary to accomplish polymerization of the treating materials on and within the fibers which are to be treated, a conventional catalyst (for example, Zn(BF an organic acid such as acetic acid, perfluoroacetic acid, citric acid, oxalic acid or other known APO polymerization agent) may be incorporated into the bath in catalytic amounts (usually no more than about 5 percent by weight, and preferably no more than 3 percent). The cellulosic material to be treated is then contacted with this bath composition to form a product of any desired degree of impregnation, and the impregnated product is then cured by any suitable method. Heat curing is the preferred method, but curing can be carried out at ambient room temperatures over extended time periods (several Weeks). Curing is probably accomplished by the reaction of the thiourea compounds and aziridinyl phosphine oxide to give polymers containing phosphorus, nitrogen and sulfur which are bound to the cellulosic materials by reaction of the'aziridinyl rings'with the cellulosic hydroxyl groups, or other reactive substituents.

If the cellulosic material which is to be treated is a textile, other known conventional fabric treating agents such as fabric softeners, wetting agents and emulsifiers may be incorporated into the treating bath. Amounts of up to a total of about 10l5 percent by (dry) weight (based on the total weight of the bath) of such treating agents may be employed. Typical fabric softening agents which may be-incorporated into such a treating bath include quaternary ammonium salts such as the dimethyl benzylamine quaternary formed by combination with the reaction product of a polyethoxylated nonylphenol and epichlorohydrin, emulsified polyethylene and emulsified stearamide. Typical non-ionic wetting agents include polyoxyalkylene polyethers and hydroxy-containing polyethers such as are obtained by the reaction of alkylated phenols with 8-15 moles of ethylene oxide. In addition, other flame-proofing ingredients (for example, lower alkyl ammonium phosphates such as methyl ammonium phosphate, ethyl ammonium phosphate, etc.) may be incorporated into the treating composition. Amounts of'urea of up to about 5 percent by weight may be incorporated into the treating bath without the production of undesirable fumes.

Water is the preferred carrier for the treating mixtures, although other solvents may be used if desired. The compositions maybe heated to form a prepolyrnerprior to deposition on the cellulosic material. Typical treating bath concentrations using water as the carrier and/or solvent are summarized in Table v1 (all percentages are based upon the total weight of the bath). In addition to the ingredients listed in Table 1, a fabric softener and wetting agent was used in each bath composition. The fabric softener usedwas Moropol-700 softener (containing 30 percent by Weight of emulsified polyethylene). The concentration used 'was from 3.0 to 5.0 percent by weight based on the total Weight of the bath. The wetting agent was Dowfax 9N9 non-ionic surfactant, The concentration used was from 0.1 to 0.5 percent by weight based upon the total weight of the bath.

TABLE 1 APO (Gone. in Percent by Wt. Thiourea Compound (Percent Catalyst (Percent Based on Total by Wt. in Parenthcses) by Wt. in Wt. of Treating Parentheses) Composition) II 10-15 HgNC'NH; Zn(BF4)1 (5-15) (1. -2.

ll 15-25 HaN-C-NH: Z11(BF4)5 (-13) (1. 0-2. 5) e F -25 H3C-N'C'-NH2 Zn(BF4); (10-20) (1. 0-2. 5)

H I 15-30 HzN--CNCH:O H Zn(B F4) 2 (10-20) (1. 0-2. 5) r s 10-25 CzHs-N-CN-C1H5 No catalyst (10-25) t i a 15-30 H0 CHr-N-CNCH:O H Zn(B F), 10-25) (1. 0-2. 5

The treating bath is generally held at a temperature of from about 32 to 100 F. during the impregnation of the material to be treated.

When substituted thiourea compounds are employed, it is preferable to use N-lower alkyl (1-4 carbon atoms, methyl, ethyl, n-propyl, i-propyl, n-butyl, sec.-butyl, tertbutyl, i-butyl) or N-alkylol substituted thiourea compounds of the formula H s H wherein each of R and R is a group of the formula x is an integer of from 0 to 4 and y is an integer of from 1 to 2. Thus, when x is 2 and y is 2, compounds such as l-ethyl-3-ethylol thiourea, 1,3-diethyl thiourea and 1,3-diethylol thiourea are represented by the proper choice of the substituents R and R Other examples include 1,3-dimethyl thiourea and 1-methyl-3-n-propyl thiourea.

Any cellulose-containing material (especially textiles, paper and wood) may be treated with the bath compositions of the invention by merely impregnating the material with a treating bath (solution, mixture or dispersion) at ambient temperature containing APO and a thiourea compound, followed by curing the impregnated material at temperatures of from about 200 to 350 F. for from about 1 to 2 minutes to /2 hour (higher temperatures requiring less time). The material may be dried prior to the curing step. In ordinary commercial mill operation, the textile material to be treated is dipped in the bath once or twice followed by a squeezing or wringing operation to remove excess bath solution. The impregnated fabric is then dried and cured. The treated fabric contains from 5 to percent of APO based upon the dry weight of the fabric and from 5 to 15 percent of the thiourea compound. Typical fabrics (either woven or non-woven) which may be efiiciently rendered flame retardant according to the present invention include cotton, viscose rayon, rayon acetate, cotton blend fabrics, as well as other cellulosebased natural and synthetic textiles. Wood specimens which are treated with compositions containing APO and thiourea char when placed in a Bunsen burner flame but do not burn when the flame is removed. When wood is treated according to the invention, it is not necessary to impregnate the fibers deeply. Only an amount of APO- thiourea mixture sufficient to inhibit the burning of the surface of the wood is used.

The following examples are submitted for the purpose of illustration only and are not to be construed as limiting compound in a mole ratio of approximately 1:1, so that the solids content (based upon the total weight of the bath) of the APO-thiourea mixture was about 35 percent.-

The fabrics used were broadcloth, sateen and twill with an untreated weight per square yard of 3 /2 ounces, 8 ounces and 9 ounces, respectively. The fabrics were padded through the treating bath once and pressed once with rollers to remove excess bath fluid. The wet fabric was dried at about 240 F. for about 2 minutes and then cured for two minutes at 325 F. The treated fabric was then given a standard after wash in an automatic home laundry washer (ten gallons of water at F., /2 cup of a commercial alkylbenzene sulfonate detergent, ten minute wash cycle, followed by one spray rinse and one deep rinse). The fabrics were rated according to the hand and to the flame retardance (AATCC Standard Test 34-1952, Vertical Char test). No conditioning was given to the fabrics before testing for the vertical char, except the conditioning existing in the laboratory at the time of the test. These conditions were (1) temperature: approximately 70-75 F. and (2) relative humidity: approximately 30-40 percent.

The fabrics were given a series of four durability washes and the vertical char test was then repeated after each boil cycle. A durability wash consists of the following treatment: The fabric is washed for 45 minutes at 200- 212 F. in an agitator-type washing machine with 100 grams of soda ash (Na CO 100 grams of Ivory Flakes neutral soap and 10 grams of Tide detergent in 88 pounds of water for every 4 pounds of fabric. The washed 1 fabric is then given a 15 minute rinse in water at F.

The results are summarized in Table 2. For a fabric with a weight of from 2.0 to 6.0ounces per square yard, the maximum permissible average char. length in warp or filling direction is 5 inches and the 1 maximum length of char for any one sample is 6 /2 inches.

Similarly, for fabrics (such as twill or sateen) with a 1 weight of from 6.0 to 9.5 ounces per square yard, the maximum permissible average char length in warp or filling direction is 4 /2 inches and the maximum length of char for any one specimen is 5% inches. Fabric irregularities produce some high. values.

The following standard tests were used throughout the examples:

The vertical char test .(AATCC Test No. 34-1952) is carried out using strips of cloth 10 inches long by 2% inches wide held vertically in a standard apparatus while a preadjusted flame is applied to the bottom inch of the fabric for a fixed standard time. Average values of three samples are taken.

The Elmendorf tear. test (ASTM D-l424-56T) meassize between two parallel jaws and applying a load.

(ASTM D39-49, Section 10).

TABLE 2 Percent Total Solids (Dry wt. of APO+ Example Mole Ratio Thiourea (APO+Thiourea Fabric Thlourea Compd.)X N o. Thiourea Compound Compound:APO Cornpd.)X100+APO-I- Type 100+Dry Fabric Thiourea Comd.+ (Percent Total Add-on) Remainder of ath I (NHmOS 1:1 35.0 BBC 21.9 II 0. (NH2)2CS 1:1 35.0 OD 26. 5 III... NHmOS 1:1 38.0 BBC 23. 9 IV NH CS 1:1 38.0 OD 28.3 V (NHMCS 1:1 35.0 BBC 22.0 VI (NHmCS 1:1 35.0 D 24.9 VII- (NHmCS 1. :1 35.0 BBC 23. 4 VIII (NH:)2CS 1.5:1 35.0 OD 25.9 IX (NH2)2CS 1:1 34. 4 WBC 21. 5 X (NHghCS 1:1 34. 4 T 23.0 XL... (NHmOS 1. 5:1 34.4 WBC 20.7 XII. (NHQQCS 1.5:1 34.4 T 22.1 XIII (HOCHzN)2C=S 1.06:1 35. 7 BBC 23. 6 XIV (HOCH;N) C=S 1.06:1 35. 7 OD 28. 2

. ll XV (HO CH;N)CNH 1.25:1 35.0 BBC 20.3

H XVI (HOCHqN)C-NH2 1.25:1 35.0 OD 26. 2

TABLE 2-Continued Char Length (inches), Average of Three Runs, Maxirnums in ParenthesesNumber of Example Number Durability Washes V V 4 4 (e2) (42 (6% (a (4%) 5 2) XIII 1 xrv $6 XV A /1 r V) XVI 33 3% 3 a 3% 3% WBC=white broadcloth (33 oz. per sq. yard). BBC=belge broadcloth (3% oz. per sq. yard). OD=olive drab sateen (8 oz. per sq. yard).

'I;=twill (9 oz. per sq. yard).

Maxims. omitted from the table were not recorded.

The tear strengths and breaking strengths (both warp and fill) of the treated fabrics were excellent even after 4 durability washes.

Example XVII The following 'ingredientslwere combined to form an aqueous bath solution (all percentages by weight based on the total weight vof the bath solution).

Ingredient: Percent APO p 21.40 Thiourea 12.90 -Catalyst [Zn(BF 2.14 Fabric softener (polyethylene-type) 1.50 Dowfax 9N9 non-ionic wetting agent 0.20 Total solids 38.14

Remainder water.

Samples of white broadcloth and brown nine ounce twill were padded through the bath to a percent wet pick-up Wt. of solution on cloth Dry wt. of cloth X which corresponds to about 22.8 grams ofjsolid add-on per 100 grams of dry, untreated cloth. The fabrics were formed.

dried at about 210 F. for about 2 minutes and cured at 325 F. for 2% minutes. The treated fabrics were then given an afterwash (as in Examples I-XVI). The dried fabrics were then given successive vertical char tests after each of the four durability wash cycles. The following char lengths were obtained:

Number of Durability Washes 0 1 2 4 Length of char (inches) of broadcloth 4% 4 4% 4% 4 Length of char (inches) 018 oz. twill 3% 8% 3% 3% 3% Example XVIII I In a manner similar to that used in the preceding examples, a bath consisting of the following ingredients was prepared:

Ingredient: Grams 1) percent APO solution in CH CH OH 108 White broadcloth (3 /2 ounces per square yard) was dipped in the bath, squeezed in a roller, dried 2 minutes at 240 F. and cured for 2 minutes at 325 F. The wet pick-up was 64.5 percent, corresponding to a total dry solids pick-up of grams per grams of dry fabric. The fabric was given an afterwash as in the preceding example and dried. The char length vof the fabric by the AATCC (American Association of Textile Chemists and Colorists) vertical char test 34-1952 was 5% inches.

Example XIX Ina mill comparison of APO-thiourea and APO-urea mixtures with identical fabric softener, catalyst and nonionic wetting agent, smoke-like fumes were formed with the APO-urea mixture during the curing step. The venting system would not remove the fumes as they were No fumes were obtained with the APO-thiourea mixture.

7 Example XX A bath composition consisting of the following ingredients was prepared by simply mixing the components.

7 x 16" x A") were dipped in the freshly-prepared bath for 30 minutes, drained and weighed to determine wet pick-up. The average wet pick-up (6 samples) was percent. The drained specimens were cured for minutes at 300 F. in an oven. The treated specimens charred when placed in a luminous open flame (Bunsen burner), but would not burn when the flame was removed.

Example XXI A bath containing 31 percent by weight of an APO- thiourea mixture (mole. ratio of thiourea to APO of 1.5 :1) was prepared as follows.

Ingredient: Pounds (l) 80 percent APO in ethyl alcohol 240 (2) Thiourea 126 (3) Fabritone 23 fabric softener (an emulsi fied stearamide) (4) Dowfax 9N9 wetting agent 3 (5) Ice 50 (6) Water sufficient to bring the total volume to 115 gallons 571 Total 1035 The temperature of the bath was about 70 F. when initially prepared. The starting temperature of the water was about 100 F. and ice was used to cool the bath to 70 F. A sample of 3000 yards of Type 140 muslin (42 inches wide, mint green casing for pillowcases, approximately 3 ounces per square yard) was padded through the treating bath to an estimated wet pick-up of 75 percent. The fabric was pressed with rollers to remove excess fluid. The running speed was 75 yards per minute. Drying was accomplished with infrared preheaters and a tenter frame heated to 240 F. (A tenter frame is a conveyor equipped with parallel clips which keep the wet fabric taut while the fabric is moved through a drying oven.) The f-abricrwas cured at 330335 F. in a 150 yard curing oven. The fabric was then washed in a small amount of wetting agent, rinsed and dried. The treated fabric had excellent flame retardant characteristics as measured by AATCC Test No. 34-1952.

Example XXII A bath composed of the following ingredientswas prepared at room temperature.

Unfinished broadcloth was treated in accordance with the procedure of Examples I-XVI. The wet pick-up was about 65 percent. The percent dry add-on per 100 grams of dry fabric was 13.6 grams for the APO and 9.0 grams for the thiourea. The breaking strength (as measured according to ASTM D-39-49, Section 10) and tear strength (as measured according to ASTM D-1424-56T) I were as follows Finished Control Fabric Breaking strength (lbs):

This data indicates that no appreciable decrease in breaking strength occurs as the result of treatment, while the tear strength actually increases somewhat. In addition, the treated fabric had good flame retardanceafter four durability washes and after 50 home launderings.

Similar results were obtained using a bath composed of 21.0 percent APO, 13.6 percent thiourea, 0.64 percent Zn(BF 3.9 percent Polymul CS-41 fabric softener and 0.2 percent Triton X-lOO wetting agent, with the remainder of the bath composed of water (all percentages by weight).

As used herein, the term cellulosic is meant to include materials which contain cellulose as well as materials which are basedupon cellulose derivatives. Thus, viscose rayon (based upon the reaction of the hydroxyl groups of cellulose with carbon disulfide in the presence of NaOH to give xanthates), oxidized cellulose and rayon acetate are typical examples of cellulosic materials.

I claim as my invention:

1. Method of treating cellulosic material which comprises contacting said material with a treating bath containing from 10 to 50% by weight of a mixture of (1) tris(l-aziridinyl)phosphine oxide, and (2) a thiourea compound of the formula N s H R1I IH l I-R: wherein each of R and R is selected from the group consisting of (a) (CHfi H and f TH wherein x is an integer of from 0 to 4 and y is an integer of from 1 to 2, to form an impregnated materialand curing said impregnated material, wherein the mole ratio of (2)1(1) is from 0.3:1 to 3.011.

2. The method of claim 1 wherein the cellulosic material is a cellulose-containing fabric.

3. The method of claim 1 wherein the cellulosic material is wood. 4. A method of treating a cellulose-containing fabric which comprises: I

(1) contacting said fabric with an aqueous treating bath containing from 15 to 50 percent by weight of a mixture of (a) tris(l-aziridinyl)phosphine oxide, and (b) a compound of the formula gestural.

6. The. method'of claim 4 wherein the cellulose-containing fabric is a cotton textile. v

7. A method of treating a cellulose-containing fabric which comprises:

(1) contacting said fabric with an aqueous treating bath containing from 15 to 50 percent by weight of v a mixture of (a) tris(l-aziridinyDphosphine oxide, and (b) the compound I E HOCH2-NCNH2 wherein the mole ratio of (b):(a) is from 0.5:1 to 2.021 to form an impregnated fabric, and

(2) curing said impregnated fabric at a temperature of from about 200 to 350 F.

8. A method of treating a cellulose-based textile which comprises contacting said textile with a treating bath containing from 10 to 50 percent by Weight of a mixture of N,N'-dimethy1ol thiourea and tris(1-aziridinyl)phosphine oxide in a mole ratio of from 0.5 :1 to 20:1, respectively, to form an impregnated textile and curing said impregnated textile at a temperature of from 200 to 350 F. to produce a flame retardant product.

9. A method of flame-proofing wood which comprises contacting the Wood with a treating bath containing from 10 to 50 percent by weight of a mixture of thiourea and tris(1-aziridiny1)phosphine oxide in a mole ratio of from 0.5 :1 to 2.0:1, respectively, to form an impregnated wood product and curing said impregnated wood product at a temperature of from 200 to 350 F.

10. A treating bath for flame-proofing cellulose-containing material which comprises an aqueous solution of from 10 to 50 percent by weight of a mixture of (1) tris(1-aziridinyl)phosphine oxide, and

1 0 2) a compound of the formula II s H R1*-I I( -I 1'Ra wherein each of R and R is selected from the group consisting of (a) {CH hH and (b) 4CH OH wherein x is an integer of from 0 to 4 and y is an integer of from 1 to 2 and wherein the mole ratio of (2):(1) is from 0.3:1 to 30:1.

11. A flame-retardant cellulosic material produced according to the process of claim 1.

References Cited UNITED STATES PATENTS 1,945,714 2/1934 Winogradow 117-138 2,415,113 2/1947 Seymour et a1. 117-137 2,440,202 4/1948 Klaber et a1.

2,725,311 11/1955 Kenaga et a1 117-136 2,803,562 8/1957 Erbel et a1. 117-137 X 2,859,134 11/1958 Reeves et a1 117-136 2,891,877 6/1959 Chance et al. 117-136 3,085,029 4/1963 Miles et al. 117-143 X 2,772,188 11/1956 Reeves et al. 117-136 WILLIAM D. MARTIN, Primary Examiner. T. G. DAVIS, Assistant Examiner. 

